Merge pull request #2859 from nanoant/patch/norewrite-pragma

{.noRewrite.} pragma for term rewriting

compiler/ast.nim

@@ -423,6 +423,7 @@ type
                 # but unfortunately it has measurable impact for compilation
                 # efficiency
     nfTransf,   # node has been transformed
+    nfNoRewrite # node should not be transformed anymore
     nfSem       # node has been checked for semantics
     nfLL        # node has gone through lambda lifting
     nfDotField  # the call can use a dot operator

compiler/parser.nim

@@ -64,6 +64,7 @@ proc setBaseFlags*(n: PNode, base: TNumericalBase)
 proc parseSymbol*(p: var TParser, allowNil = false): PNode
 proc parseTry(p: var TParser; isExpr: bool): PNode
 proc parseCase(p: var TParser): PNode
+proc parseStmtPragma(p: var TParser): PNode
 # implementation
 
 proc getTok(p: var TParser) =
@@ -499,10 +500,13 @@ proc parsePar(p: var TParser): PNode =
   #| parKeyw = 'discard' | 'include' | 'if' | 'while' | 'case' | 'try'
   #|         | 'finally' | 'except' | 'for' | 'block' | 'const' | 'let'
   #|         | 'when' | 'var' | 'mixin'
-  #| par = '(' optInd (&parKeyw complexOrSimpleStmt ^+ ';'
-  #|                  | simpleExpr ('=' expr (';' complexOrSimpleStmt ^+ ';' )? )?
-  #|                             | (':' expr)? (',' (exprColonEqExpr comma?)*)?  )?
-  #|         optPar ')'
+  #| par = '(' optInd
+  #|           ( &parKeyw complexOrSimpleStmt ^+ ';'
+  #|           | ';' complexOrSimpleStmt ^+ ';'
+  #|           | pragmaStmt
+  #|           | simpleExpr ( ('=' expr (';' complexOrSimpleStmt ^+ ';' )? )
+  #|                        | (':' expr (',' exprColonEqExpr     ^+ ',' )? ) ) )
+  #|           optPar ')'
   #
   # unfortunately it's ambiguous: (expr: expr) vs (exprStmt); however a
   # leading ';' could be used to enforce a 'stmt' context ...
@@ -521,6 +525,8 @@ proc parsePar(p: var TParser): PNode =
     getTok(p)
     optInd(p, result)
     semiStmtList(p, result)
+  elif p.tok.tokType == tkCurlyDotLe:
+    result.add(parseStmtPragma(p))
   elif p.tok.tokType != tkParRi:
     var a = simpleExpr(p)
     if p.tok.tokType == tkEquals:

compiler/patterns.nim

@@ -130,7 +130,9 @@ proc matchNested(c: PPatternContext, p, n: PNode, rpn: bool): bool =
 
 proc matches(c: PPatternContext, p, n: PNode): bool =
   # hidden conversions (?)
-  if isPatternParam(c, p):
+  if nfNoRewrite in n.flags:
+    result = false
+  elif isPatternParam(c, p):
     result = bindOrCheck(c, p.sym, n)
   elif n.kind == nkSym and p.kind == nkIdent:
     result = p.ident.id == n.sym.name.id

compiler/pragmas.nim

@@ -37,7 +37,7 @@ const
     wImportc, wExportc, wNodecl, wMagic, wDeprecated, wBorrow, wExtern,
     wImportCpp, wImportObjC, wError, wDiscardable, wGensym, wInject, wRaises,
     wTags, wLocks, wGcSafe}
-  exprPragmas* = {wLine, wLocks}
+  exprPragmas* = {wLine, wLocks, wNoRewrite}
   stmtPragmas* = {wChecks, wObjChecks, wFieldChecks, wRangechecks,
     wBoundchecks, wOverflowchecks, wNilchecks, wAssertions, wWarnings, wHints,
     wLinedir, wStacktrace, wLinetrace, wOptimization, wHint, wWarning, wError,
@@ -859,6 +859,8 @@ proc singlePragma(c: PContext, sym: PSym, n: PNode, i: int,
             c.module.flags.incl sfExperimental
           else:
             localError(it.info, "'experimental' pragma only valid as toplevel statement")
+        of wNoRewrite:
+          noVal(it)
         else: invalidPragma(it)
       else: invalidPragma(it)
   else: processNote(c, it)

compiler/semstmts.nim

@@ -1268,6 +1268,8 @@ proc semPragmaBlock(c: PContext, n: PNode): PNode =
     of wLocks:
       result = n
       result.typ = n.sons[1].typ
+    of wNoRewrite:
+      incl(result.flags, nfNoRewrite)
     else: discard
 
 proc semStaticStmt(c: PContext, n: PNode): PNode =

compiler/wordrecg.nim

@@ -55,7 +55,7 @@ type
     wFloatchecks, wNanChecks, wInfChecks,
     wAssertions, wPatterns, wWarnings,
     wHints, wOptimization, wRaises, wWrites, wReads, wSize, wEffects, wTags,
-    wDeadCodeElim, wSafecode, wNoForward,
+    wDeadCodeElim, wSafecode, wNoForward, wNoRewrite,
     wPragma,
     wCompileTime, wNoInit,
     wPassc, wPassl, wBorrow, wDiscardable,
@@ -139,7 +139,7 @@ const
 
     "assertions", "patterns", "warnings", "hints",
     "optimization", "raises", "writes", "reads", "size", "effects", "tags",
-    "deadcodeelim", "safecode", "noforward",
+    "deadcodeelim", "safecode", "noforward", "norewrite",
     "pragma",
     "compiletime", "noinit",
     "passc", "passl", "borrow", "discardable", "fieldchecks",